This invention is generally in the field of process equipment and methods for making particles, and more particularly to methods of deagglomerating or grinding spray dried particles.
Spray drying is commonly used in the production of particles for many applications, including pharmaceuticals, food, cosmetics, fertilizers, dyes, and abrasives. Spray drying can be tailored to create a wide spectrum of particle sizes, including microparticles. Spray dried particles are useful in a variety of biomedical and pharmaceutical applications, such as the delivery of therapeutic and diagnostic agents, as described for example in U.S. Pat. No. 5,853,698 to Straub et al.; U.S. Pat. No. 5,855,913 to Hanes et al.; and U.S. Pat. No. 5,622,657 to Takada et al. For these applications, microparticles having very specific sizes and size ranges often are needed in order to effectively deliver the active agents.
Particles may tend to agglomerate during their production and processing, thereby undesirably altering the effective size of the particles, to the detriment of the particle formulation's performance and/or reproducibility. In other circumstances, the particles made may simply be larger than desired for a particular application. Therefore, after they are produced, particles may require additional processing for size reduction and/or deagglomeration.
In one common approach, separate batch process steps are used. For example, particles are made by a known spray drying process, collected, and then ground in a second, separate step. Such a batch method, however, undesirably requires the use of a transfer step from the spray dryer to the mill, which, for an aseptic process, may be difficult to perform. Such a batch process also requires two separate collection steps that are both associated with a yield loss. It would be desirable to provide a sterile particle production and milling process and to minimize product yield losses, reduce material transfer steps, reduce process time, and reduce production costs. In addition, laboratory scale methods for producing microparticle pharmaceutical formulations may require several steps, which may not be readily or efficiently transferred to larger scale production. It would be desirable for the microparticle production and deagglomeration (or grinding) process to be adaptable for efficient, cost effective, commercial scale production.